From fork-admin@xent.com Wed Oct 2 18:18:54 2002 Return-Path: Delivered-To: yyyy@localhost.example.com Received: from localhost (jalapeno [127.0.0.1]) by jmason.org (Postfix) with ESMTP id E68B216F03 for ; Wed, 2 Oct 2002 18:18:52 +0100 (IST) Received: from jalapeno [127.0.0.1] by localhost with IMAP (fetchmail-5.9.0) for jm@localhost (single-drop); Wed, 02 Oct 2002 18:18:52 +0100 (IST) Received: from xent.com ([64.161.22.236]) by dogma.slashnull.org (8.11.6/8.11.6) with ESMTP id g92GpiK17868 for ; Wed, 2 Oct 2002 17:51:48 +0100 Received: from lair.xent.com (localhost [127.0.0.1]) by xent.com (Postfix) with ESMTP id 7E5B7294176; Wed, 2 Oct 2002 09:47:02 -0700 (PDT) Delivered-To: fork@example.com Received: from barry.mail.mindspring.net (barry.mail.mindspring.net [207.69.200.25]) by xent.com (Postfix) with ESMTP id 8E1E7294175 for ; Wed, 2 Oct 2002 09:46:13 -0700 (PDT) Received: from user-119ac86.biz.mindspring.com ([66.149.49.6]) by barry.mail.mindspring.net with esmtp (Exim 3.33 #1) id 17wmdg-0005BM-00; Wed, 02 Oct 2002 12:46:20 -0400 MIME-Version: 1.0 X-Sender: rahettinga@pop.earthlink.net Message-Id: To: Digital Bearer Settlement List , fork@example.com From: "R. A. Hettinga" Subject: Re: Optical analog computing? Content-Type: text/plain; charset="us-ascii" Sender: fork-admin@xent.com Errors-To: fork-admin@xent.com X-Beenthere: fork@example.com X-Mailman-Version: 2.0.11 Precedence: bulk List-Help: List-Post: List-Subscribe: , List-Id: Friends of Rohit Khare List-Unsubscribe: , List-Archive: Date: Wed, 2 Oct 2002 10:37:02 -0400 X-Spam-Status: No, hits=-3.9 required=5.0 tests=AWL,KNOWN_MAILING_LIST,QUOTED_EMAIL_TEXT, RCVD_IN_MULTIHOP_DSBL,RCVD_IN_UNCONFIRMED_DSBL, SIGNATURE_SHORT_DENSE version=2.50-cvs X-Spam-Level: --- begin forwarded text Status: RO Date: Wed, 02 Oct 2002 01:30:24 -0400 From: "John S. Denker" Subject: Re: Optical analog computing? Sender: jsd@no.domain.spam To: "R. A. Hettinga" Cc: Digital Bearer Settlement List , cryptography@wasabisystems.com "R. A. Hettinga" wrote: ... > "the first computer to crack enigma was optical" > "the first synthetic-aperture-radar processor was optical" > "but all these early successes were classified -- 100 to 200 projects, > and I probably know of less than half." > > --> Do these claims compute?! is this really a secret history, or does > this mean holography, of am I just completely out of the loop?1 Gimme a break. This is remarkable for its lack of newsworthiness. 1) Bletchley Park used optical sensors, which were (and still are) the best way to read paper tape at high speed. You can read about it in the standard accounts, e.g. http://www.picotech.com/applications/colossus.html 2) For decades before that, codebreakers were using optical computing in the form of superposed masks to find patterns. You can read about it in Kahn. 3) People have been doing opto-electronic computing for decades. There's a lot more to it than just holography. I get 14,000 hits from http://www.google.com/search?q=optical-computing > Optical info is a complex-valued wave (spatial frequency, amplitude and > phase) It isn't right to make it sound like three numbers (frequency, amplitude, and phase); actually there are innumerable frequencies, each of which has its own amplitude and phase. > lenses, refractions, and interference are the computational operators. > (add, copy, multiply, fft, correlation, convolution) of 1D and 2D arrays > > and, of course, massively parallel by default. > > and, of course, allows free-space interconnects. Some things that are hard with wires are easy with light-waves. But most things that are easy with wires are hard with light-waves. > Here's a commercialized effort from israel: a "space integrating > vector-matric multiplier" [ A ] B = [ C ] > laser-> 512-gate modulator -> spread over 2D > "256 Teraflop equivalent" for one multiply per nanosecond. People were doing smaller versions of that in the 1980s. > Unclassified example: acousto-optic spectrometer, 500 Gflops equivalent > (for 12 watts!) doing continuous FFTs. Launched in 1998 on a 2-year > mission. Submillimeter wave observatory. Not "FFTs". FTs. Fourier Transforms. All you need for taking a D=2 Fourier Transform is a lens. It's undergrad physics-lab stuff. I get 6,000 hits from: http://www.google.com/search?q=fourier-optics > Of course, the rest of the talk is about the promise of moving from > optoelectronic to all-optical processors (on all-optical nets & with > optical encryption, & so on). All optical??? No optoelectronics anywhere??? That's medicinal-grade pure snake oil, USP. Photons are well known for not interacting with each other. It's hard to do computing without interactions. --- end forwarded text -- ----------------- R. A. Hettinga The Internet Bearer Underwriting Corporation 44 Farquhar Street, Boston, MA 02131 USA "... however it may deserve respect for its usefulness and antiquity, [predicting the end of the world] has not been found agreeable to experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'